On Mon, 2022-03-14 at 21:07 +0100, Niels Dossche wrote:
> ceph_add_cap says in its function documentation that the caller should
> hold the read lock on the session snap_rwsem. Furthermore, not only
> ceph_add_cap needs that lock, when it calls to ceph_lookup_snap_realm it
> eventually calls ceph_get_snap_realm which states via lockdep that
> snap_rwsem needs to be held. handle_cap_export calls ceph_add_cap
> without that mdsc->snap_rwsem held. Thus, since ceph_get_snap_realm
> and ceph_add_cap both need the lock, the common place to acquire that
> lock is inside handle_cap_export.
>
> Signed-off-by: Niels Dossche <dossche.niels@xxxxxxxxx>
> ---
> fs/ceph/caps.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> index b472cd066d1c..0dd60db285b1 100644
> --- a/fs/ceph/caps.c
> +++ b/fs/ceph/caps.c
> @@ -3903,8 +3903,10 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex,
> /* add placeholder for the export tagert */
> int flag = (cap == ci->i_auth_cap) ? CEPH_CAP_FLAG_AUTH : 0;
> tcap = new_cap;
> + down_read(&mdsc->snap_rwsem);
> ceph_add_cap(inode, tsession, t_cap_id, issued, 0,
> t_seq - 1, t_mseq, (u64)-1, flag, &new_cap);
> + up_read(&mdsc->snap_rwsem);
>
> if (!list_empty(&ci->i_cap_flush_list) &&
> ci->i_auth_cap == tcap) {
Looks good. The other ceph_add_cap callsites already hold this.
Merged into ceph testing branch.
Thanks!
--
Jeff Layton <jlayton@xxxxxxxxxx>
